Wound healing device

ABSTRACT

A plasma coating device for treating a wound comprises a plasma chamber having: one or more electrodes, a gas supply inlet, a plasma outlet exposed to ambient pressure, and an ignition system operatively connected to the electrodes for providing a non-thermal equilibrium plasma within the plasma chamber. An aerosol delivery system is operable to introduce a bioresorbable material as an aerosol into the plasma, to produce a coating on the wound surface.

BACKGROUND

Electrical plasma devices are well established in medicine. For example,Massarweh et al, J. Am. Coll. Surg., 2006, 202 (3), 520, disclosesplasma devices for surgery; Reich et al, European Urology, 2003, 44 (2),272-276, describe the use of an argon plasma (APC) to coagulate bloodand stop bleeding; and Mennel et al, Experimental and ToxicologicalPathology, 2002, 54 (3), 255, disclose using a helium plasma to obtain asimilar response to the APC technique.

Plasmas can also be used to sterilise skin as disclosed in G. Fridman,A. D. Brooks, M. Balasubramanian, A. Fridman. A. Gustol, V. N. Vasilets,H. Ayan, G. Friedman, Plasma Process. Polym. 4 (2007) 370) andWO2006/116252. The use of plasma devices to promote wound healing hasalso been disclosed in US2008/0237484 and in WO2009/101143.

Outside of medicine, plasma devices are widely used to produce thin filmcoatings in industrial applications. Plasma polymers offer a number ofadvantages over conventional polymer coatings. The combination ofreactive plasma and chemically active monomers produces a coating thatis uniform, pin hole free and well bonded to the substrate. Furthermore,the curing can occur in a manner that is almost instantaneous, offeringnumerous processing advantages.

U.S. Pat. No. 4,929,319 describes a method for depositing a polymercoating in which an aerosol is introduced into a corona plasma and thereactive species thereby generated are allowed to deposit in a substratethat is also brought into the corona plasma.

WO 02/28548 describes a process in which an aerosol is introduced intoan atmospheric pressure glow discharge (APGD) plasma and a coating isthereby formed on a substrate. The coating chemistry was found to bevirtually unchanged from that of the precursor molecules by the exposureto the homogeneous APGD plasma.

WO2005/106477 describes a process for coating a substrate with abiomolecule in which the substrate is placed between two electrodes anda plasma is generated by applying an alternating current in which apositive voltage is applied to the first electrode and a zero voltage tothe second electrode, and then a zero voltage to the first electode anda negative voltage to the second electrode. A coating is then applied byintroducing a reactive precursor to form a coating and biomolecules aresimultaneously immobilised. The biomolecules may be introduced as anaerosol.

WO 05/110626 discloses coating a substrate with a polymer layercontaining active agents. The method involves exposing a mixture ofpolymer forming materials (which react to form chemical bonds in aplasma) and active agents (which do significantly react in the plasma)to plasma. The polymer forming materials listed include variousacrylates, alkenes and dienes that can be polymerised by the reactivespecies present within a plasma.

These prior documents rely on the plasma to induce the polymerisation ofa monomer to produce the thin film or coating. The polymerisation can bedriven through free radical (A. Bogaerts et al., Spectrochimica ActaPart B, 57 (2002) 609-658) or cationic reaction mechanisms (Daniel C.Guerin, David D. Hinshelwood, Sorin Monolache, Ferencz S. Denes, andVasgen A. Shamamian, Langmuir, 2002, 18 (10), pp 4118-4123).

Thus, while the methods described in WO 05/106477 and WO 05/110626 doallow for the deposition of polymers containing active agents, they arereliant upon the presence of a precursor which can react in the plasmato form the polymer coating during the deposition process. Therequirement to induce reactions within the polymer precursor withoutdamaging the active agent limits the degree of polymerisation that canbe achieved.

SUMMARY OF THE INVENTION

The present invention provides a plasma device as claimed in claim 1.

In a further aspect, there is provided a non-thermal plasma treatedbioresorbable material for use in coating a wound as claimed in claim14.

In a still further aspect there is provided a method of treating a woundaccording to claim 22.

In embodiments of the present invention, a non-thermal plasma is appliedto a wound. The plasma can sterilise the area, coagulate blood anddeposit a bioresorbable coating to seal the wound area. The coating canfurther include active compounds to aid in wound healing.

The bioresorbable material can include blood plasma, chitosan orcollagen, but may alternatively or in addition include a protein, abiopolymer (such as chitin, alginates, cellulose or hyaluronan), or asynthetic biodegradable polymer (such as poly (lactic-co-glycolic acid)(PLGA), polylactic acid, polycaprolactone, polyglactin) or a mixture ofsuch materials.

Preferably, the bioresorbable material is introduced into a non-thermalplasma as a pre-cursor in the form of an aerosol. The bioresorbablematerial pre-cursor can either be dissolved or dispersed in a suitablecarrier liquid.

Preferably, the active compound, for example, drug, enzyme, cell,protein or DNA may be either introduced into the plasma dissolved in thebioresorbable material pre-cursor or introduced separately.

In such implementations, the active compound is incorporated alongside apre-polymerised polymer which allows the polymerisation and film formingsteps to be separated out and provides a greater degree of processcontrol.

The mixture of bioresorbable material, active compound and plasmafurther interact to produce a coating on the wound surface. The woundcan either directly contact the plasma or can be placed downstream ofthe plasma chamber outlet.

In one embodiment, blood constituents are nebulised into the plasma, todeposit a layer of coagulated blood or blood plasma onto a woundsurface.

BRIEF DESCRIPTION OF THE DRAWINGS

Embodiments of the invention will now be described, by way of example,with reference to the accompanying drawing, in which:

FIG. 1 is a schematic view of a plasma device in accordance with anembodiment of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to FIG. 1, there is shown a schematic view of a plasmadevice according to an embodiment of the invention. The device includesa plasma chamber 1 including a metal electrode 6 to which a high voltagepower supply/ignition system 2 is operatively connected. The chamber 1further includes a gas inlet port 3 through which a supply of gas, forexample, helium, argon or nitrogen or mixtures thereof is fed inoperation of the device and which in combination with the ignitionsystem causes a plasma to be struck and to stream from an outlet 8 ofthe plasma chamber. In the illustrated embodiment, a liquid deliverysystem 4 is operatively connected to an inlet of the plasma chamber andan internal nebuliser 5 causes the supplied liquid to be sprayed 7 intothe chamber 1 as an aerosol. In alternative embodiments, not shown, anexternal nebuliser feeds the aerosol to a region outside the plasmachamber where it interacts with the reactive species emanating from theoutlet 8 of the plasma chamber before coating a wound over which theplasma device is being passed.

In embodiments of the present invention, the plasma device initiallysterilises and coagulates the wound. Then, by providing an aerosol fromthe supply 4 containing a bioresorbable material which may also containan active agent, and introducing that aerosol into a plasma chamber 1,or into the reactive species that exist downstream of the plasma chamber1, the device produces a coating on the wound. If required, thesterilisation, coagulation and coating deposition can occursimultaneously. Deposition of such a coating enables the continuousinteraction of the pro-healing materials with the wound and provides forenhanced wound healing. Furthermore, the coating seals the wound andlimits the opportunity for further bacteria to infect the wound site.

The term wound can be taken to encompass all forms of damage to the skinor body including burns, cuts, tears, piercings, contusions, abrasions,lacerations, punctures, gun shots or other forms of injury to the body.It may also encompass infections or chronic wounds such as ulcers.

The invention described herein allows the introduction of bioresorbablematerial including: proteins such as collagen, fibrin or fibronecin;biopolymers such as hyaluronan, chitosan, alginates and cellulose; andalso biodegradable synthetic polymers such as PLGA which do not formusing the same vinyl polymerisation reactions favoured by conventionalplasma reactions onto a wound site. The plasma may cross-link thesematerials to produce a dry coating, but the degree of cross-linking islimited and is not sufficient to alter the functionality of thedeposited material.

Embodiments of the present invention employ non-thermal plasma deviceswhere the plasma operates close to room temperature thus allowing theprocessing of temperature sensitive materials, without imposing adamaging thermal burden onto the material. Nonetheless, the hotelectrons of the plasma create, through high-energy collisions, a richsource of radicals and excited species with a high chemical potentialenergy capable of chemical and physical reactivity. Non-thermalequilibrium plasmas can be created at ambient pressure and have beenreviewed extensively by Roth (Roth J. R., Industrial Plasma Engineering,Volume 2 Applications to Non-thermal Plasma Processing, Institute ofPhysics Publishing, 2001, pages 37-73). Such plasmas include dielectricbarrier discharges. Another non-thermal equilibrium plasma is theAtmospheric pressure glow discharge (APGD) as described by Okazaki et al(J. Phys. D: Appl. Phys., 26, 889-892 (1993)). These APGD plasmas havebeen described extensively by Roth as One Atmosphere Uniform GlowDischarge Plasmas (OUAGDP) and are found to operate from 0.5 to 40 kHz.Corona plasma devices can also operate in non-thermal equilibrium mode.Various plasma jets are also capable of operating in a “cold” ornon-thermal equilibrium mode.

Embodiments of the present invention employ plasma devices operating atfrequencies above 100 kHz, which is beyond the sensory threshold of apatient's nervous system. For optimum control, the plasma is operatedbelow 500 kHz and may be pulsed on and off in a controlled fashion tominimise the energy delivered to the aerosol and patient. This enablescontrolled plasma reactions that preserve precursor functionality and donot damage or fragment sensitive active species.

Alternatively, the plasma can be contained between two electrodes, witha grounded electrode separating the person or object to be treated fromthe plasma, such that no significant voltage is applied to any object orperson placed downstream of the device. This can be accomplished using aplasma device such as described by Ladwig et al (Surface & CoatingsTechnology 201 (2007) 6460-6464). Use of such a plasma device wouldallow the plasma to operate at frequencies below 100 kHz.

The plasma parameters (electrode design, frequency, voltage, gascomposition, etc.) can be chosen to control the plasma process andensure that the plasma operates in a non-thermal manner to produce alow-temperature plasma, which does not adversely affect temperaturesensitive materials which are being deposited.

Furthermore, the precursor can be introduced downstream of the plasmachamber outlet to minimise damage to the coating forming materials. Thisallows coatings containing materials sensitive to temperature, ions,free radicals and other active species present in the plasma to bedeposited where they would otherwise be damaged if introduced directlyinto the plasma chamber.

Various active compounds can be incorporated into the coating producedby this device. These can include anti-cancer drugs, anti-inflammatorydrugs, immuno-suppressants, antibiotics, antimicrobials, heparin, afunctional protein, a regulatory protein, structural proteins,oligo-peptides, antigenic peptides, nucleic acids, immunogens,glycosaminoglycans and combinations thereof.

Other active compounds include polypeptides, polyglycans, hormones,lipids, interferons, cartilage, therapeutic biologic agents bothcellular and synthetically derived, autologous, homologous andallographic and zenographic biologic agents, autologous or homologous,recombinant and synthetic derived blood cells and products containingantimicrobial/antibiotic agents, bacteriostatic agents, stem cells,stromal cells; fibroblast derived Human Dermal Collagen, matrixproteins, growth factors and cytokines, fibronectin, cells found inloose connective tissue such as endothelial cells, cells found inadipose tissue, macrophages/monocytes, adipocytes, pericytes, reticularcells found in bone marrow stroma and cultured autologous keratinocytes.

In a preferred application, the wound is coated with a layer of eithercoagulated blood or blood extracts. The coating is produced bynebulising a supply of blood, or blood constituents, into the plasmachamber or into the species exiting from the plasma chamber. This offersa route to producing thin films, which are highly biocompatible andalready contain the necessary factors (fibrin, cytokines, etc.)necessary to seal the wound and to induce wound healing.

Nonetheless, the nature of the deposited layer may be varied dependenton factors including: the underlying cause of the wound, thecharacteristics of the wound, the stage of wound healing, the particularpatient needs and risk factors, availability of autologous materials.

Thus, different depositions can be used depending on whether woundhealing is at the haemostasis, inflammation, proliferation/granulationor maturation/remodelling phase. Examples of materials for the variousphases of wound healing include:

-   -   1. Fresh trauma/burns: Seal/contain wound with a temporary        resorbable material containing appropriate active agents        including, for example, antimicrobials, analgesics,        vasoconstrictors in order to contain the wound while minimising        dehydration/shock, pain, blood loss, risk of        infection/contamination, further tissue loss, etc and initiating        haemostasis.    -   2. Haemostasis stage: A resorbable material such as blood plasma        or platelets including active agent(s) such as,        vasoconstrictors, adenosine diphosphate (ADP), thrombin,        fibrinogen/fibrin, cytokines (PDGF), chemotactic factors,        chemocines or coagulation factors.    -   3. Inflammation stage: A resorbable material such as blood        plasma including, for example, neutrophils, monocytes,        phagocytes, mast cells, proteolytic enzymes, leukocytes.    -   4. Proliferation/granulation stage: A resorbable material        including for:        -   a. Granulation—macrophages, Fibroblastic Growth Factor            (FGF), Epidermal Growth Factor (EGF), transforming growth            factor beta (TGF-beta), Extra cellular matrix (ECM),            fibroblasts, myofibroblasts        -   b. Contracture—fibroblasts, collagen, endothelial cells,            keratinocytes, angiocytes, neurocytes,        -   c. Epithelisation—growth factors, fibrin, collagen, and            fibronectin    -   5. Maturation/remodelling: Type I collagen.    -   6. Enhanced/accelerated wound healing or for large wound and        burn injuries or chronic non-healing ulcers: Cytokines and        growth factors

Other applications including cornea regeneration using cytokinesfollowing abrasion or cataract treatment.

All variants may also provide the following:

-   -   A moisture retaining occlusive barrier and high humidity at the        wound surface;    -   Gaseous exchange;    -   Thermal insulation; and    -   Protection against secondary infection

Examples 1. Deposition of Blood Plasma Coating

A biocompatible coating was deposited on to a glass slide using anon-thermal plasma discharge and blood plasma as the precursor. Theplasma discharge was created by applying an alternating voltage to acorona needle electrode assembly within a dielectric housing. Thevoltage was applied at a frequency of 100 kHz from a Redline G2000 highvoltage power supply. Helium was used as a ballast gas at a flow rate of14 litres/minute. (It will be appreciated that other gases includingargon or nitrogen or mixtures thereof could also be used.) The bloodplasma extract was nebulised into the plasma using a Burgener pneumaticnebuliser (Burgener Research, Canada) at a flow rate of 51microlitres/min. The input power was applied using a 45% duty cycle(ratio of time on to time off) and a selected input power on the powersupply of 107 V. This corresponded to an actual applied voltage of 12.7kV (pk-pk) applied to the electrodes. The substrate was a glass slideplaced approximately 5 mm downstream of the plasma exit.

The blood plasma was sprayed through the plasma and landed upon theglass slide, where it coagulated instantly to form a coating. Afterdeposition, the coating was inspected at a magnification of 40× and theviable cell numbers were counted. Prior to being exposed to theelectrical discharge, cell viability was estimated to be 90%. Afterundergoing nebulisation and plasma coagulation, over 70% of the cellswere still deemed viable, indicating that biological materials have beensuccessfully deposited intact and capable of participating in abiological healing process.

2.Deposition of a Biopolymer (Chitosan)

Chitson is known to have antimicrobial properties and is also a commonscaffold material used in regenerative medicine. Water-soluble chitosanwas dissolved in deionised water to give a concentration of 20 mg/ml.This liquid was introduced at 50 μL/min into the equipment described inExample 1 and coatings were deposited onto glass slides. Coatings weredeposited at a power input setting of 170V and 150 kHz and for times of45 seconds, 1 minute and 3 minutes. In each case, a clear coating wasdetected on the surface of the glass slide. This coating was not removedby wiping with a tissue, indicating that the coating was dry, cured andadherent.

3. Deposition of a Protein Solution (Collagen) at Low Frequency

Collagen is a known aid in wound healing process and is a key componentof skin. A plasma device comprising a needle corona electrode powered bya 100W Plasma Technics Inc power supply operating at c. 20 kHz wasprovided. Helium was introduced to the system at a rate of 8litres/minute. An acidified solution of collagen (3.8 mg/ml) wasnebulised into the resultant discharge at a flow rate of 50 μL/min andcoatings were deposited onto glass slides for 1-2 minutes. All depositswere found to be coherent, dry and adhered well to the substrate,indicating that a cured coating had been formed.

4. Deposition of a Protein Solution (Collagen) at High Frequency

A solution of collagen (1 mg/ml) was introduced into the equipmentdescribed in Example 1. The plasma was operated at 115V input power, 148kHz and a duty cycle of 44%. Helium was introduced at a rate of 5litres/min. The collagen solution was introduced at a rate of 50 μL/minand a coating was deposited onto polished Si wafers for either oneminute or two minutes. Ellipsometry detected a coating with a thicknessof 50 nm for the one minute sample and 140 nm for the two minute sample,confirming that a coating had been deposited.

1. A plasma coating device for treating a wound comprising a plasmachamber (1) having: one or more electrodes (6), a gas supply inlet (3),a plasma outlet (8) exposed to ambient pressure, and a ignition system(2) operatively connected to said electrodes for providing a non-thermalequilibrium plasma within the plasma chamber; and characterized in thatsaid device comprises an aerosol delivery system (5) operable tointroduce a bioresorbable material as an aerosol (7) into the plasma, toproduce a coating on the wound surface.
 2. A plasma coating deviceaccording to claim 1 in which said aerosol delivery system is arrangedto provide said aerosol into the plasma chamber.
 3. A plasma coatingdevice according to claim 1 in which said aerosol delivery system isarranged to provide said aerosol into a region containing reactivespecies emanating from said plasma chamber outlet.
 4. A plasma coatingdevice according to claim 1 in which said aerosol delivery system isarranged to contain a bioresorbable material pre-cursor either dissolvedor dispersed in a carrier liquid.
 5. A plasma coating device as claimedin claim 1 wherein said ignition system is arranged to provide power tosaid plasma at a frequency of at least 100 kHz.
 6. A plasma coatingdevice as claimed in claim 1 wherein said ignition system is arranged toprovide power to said plasma at a frequency of between 100 kHz and 500kHz.
 7. A plasma coating device as claimed in claim 1 wherein saidignition system is arranged to pulse said plasma.
 8. A plasma coatingdevice as claimed in claim 1 further comprising a ground electrodedisposed between the plasma chamber outlet and the wound to be treated.9. A plasma coating device as claimed in claim 1 wherein the plasma isone of a dielectric barrier discharge; an atmospheric pressure glowdischarge, a corona plasma or a plasma jet.
 10. A plasma coating deviceas claimed in claim 1 wherein said aerosol delivery system is arrangedto supply said aerosol to said wound after a period of treating thewound with only said plasma.
 11. A plasma coating device as claimed inclaim 1 further comprising means for providing an active compound tosaid wound in conjunction with said plasma treated bioresorbablematerial.
 12. A plasma coating device as claimed in claim 11 whereinsaid active compound is either dissolved in the bioresorbable materialpre-cursor or introduced separately to the plasma
 13. A plasma coatingdevice as claimed in claim 1 further comprising a gas supply arranged toprovide a supply of helium, argon, nitrogen or mixtures thereof to saidchamber.
 14. A non-thermal equilibrium plasma treated bioresorbablematerial for use in coating a wound.
 15. A material for use in coating awound as claimed in claim 14 wherein the bioresorbable material is abiopolymer, a biodegradable polymer, a protein or a mixture thereof. 16.A material for use in coating a wound as claimed in claim 15 comprisinga protein including collagen, fibrin or fibronecin; a biopolymerincluding chitin, hyaluronan, chitosan, alginates or cellulose; or abiodegradable polymer including PLGA, polylactic acid, polycaprolactoneor polyglactin.
 17. A material for use in coating a wound as claimed inclaim 14 comprising one of: blood, blood plasma or a blood constituent.18. A material for use in coating a wound as claimed in claim 14 furthercomprising one of a pharmaceutical agent or a biologically activecompound or combinations thereof.
 19. A material for use in coating awound as claimed in claim 18 comprising one or more of a drug, enzyme,cell, protein or DNA.
 20. A material for use in coating a wound asclaimed in claim 14 further including one or more of anti-cancer drugs,anti-inflammatory drugs, immuno-suppressants, antibiotics,antimicrobials, heparin, a functional protein, a regulatory protein,structural proteins, oligo-peptides, antigenic peptides, nucleic acids,immunogens, glycosaminoglycans.
 21. A material for use in coating awound as claimed in claim 14 further including one or more ofpolypeptides, polyglycans, hormones, lipids, interferons, cartilage,therapeutic biologic agents both cellular and synthetically derived,autologous, homologous and allographic and zenographic biologic agents,autologous or homologous, recombinant and synthetic derived blood cellsand products containing antimicrobial or antibiotic agents,bacteriostatic agents, stem cells, stromal cells; fibroblast derivedHuman Dermal Collagen, matrix proteins, growth factors and cytokines,fibronectin, cells found in loose connective tissue such as endothelialcells, cells found in adipose tissue, macrophages, monocytes,adipocytes, pericytes, reticular cells found in bone marrow stroma orcultured autologous keratinocytes.
 22. A method of treating a woundcomprising: providing a plasma coating device as claimed in claim 1 andapplying a non-thermal equilibrium plasma treated bioresorbable materialto coat the wound.
 23. A method according to claim 22 wherein the woundcomprises a fresh trauma or a burn and wherein the bioresorbablematerial contains one or more of an antimicrobial compound, an analgesicor vasoconstrictors.
 24. A method according to claim 22 wherein thewound is at a haemostasis stage and wherein said bioresorbable materialcomprises either blood plasma or platelets including one or more ofvasoconstrictors, adenosine diphosphate, thrombin, fibrinogen, fibrin,cytokines, chemotactic factors, chemocines or coagulation factors.
 25. Amethod according to claim 22 wherein the wound is at an inflammationstage and wherein said bioresorbable material comprises blood plasmaincluding one or more of neutrophils, monocytes, phagocytes, mast cells,proteolytic enzymes or leukocytes.
 26. A method according to claim 22wherein the wound is at a granulation stage and wherein saidbioresorbable material includes one or more of macrophages, FibroblasticGrowth Factor, Epidermal Growth Factor, transforming growth factor beta,extra cellular matrix, fibroblasts or myofibroblasts.
 27. A methodaccording to claim 22 wherein the wound is at a contracture stage andwherein said bioresorbable material includes one or more of fibroblasts,collagen, endothelial cells, keratinocytes, angiocytes or neurocytes.28. A method according to claim 22 wherein the wound is at anepithelisation stage and wherein said bioresorbable material includesone or more of growth factors, fibrin, collagen or fibronectin.
 29. Amethod according to claim 22 comprising remodelling a wound and whereinsaid bioresorbable material comprises type I collagen.
 30. A methodaccording to claim 22 comprising treating a large wound, burn injury orchronic non-healing ulcer and wherein said bioresorbable materialcomprises cytokines and growth factors.
 31. A method according to claim22 comprising re-generating a cornea and wherein said bioresorbablematerial comprises cytokines.